1. Field of the Invention
The present invention is directed to uninterruptible power supplies and more particularly to a circuit for synchronizing the transfer of an alternating current to a load between an inverter supplying an alternating current from a storage source of direct current and an alternating current power line source.
2. Description of the Prior Art
In today's wide use of computers, data processors, controllers, etc. in data processing systems, it is extremely critical that the system be supplied with continuous power during its operation. Due to inadequate capacity and increasing load demands, commercially-supplied power is often subject to complete failure of the power signals or a reduction in the magnitude of the available voltage during peak demand periods. In cases where various customers subject the power system to sudden electrical loads, transients are generated in the system affecting the magnitude and phase of the supplied power signal.
Since the storage of data in a computer system is predicated on the continuous operation of the computer, power interruptions can adversely affect the integrity of the stored data. When the power drops abruptly, the computer will terminate operation probably with a high possibility of component damage. In order to overcome this situation, computers operating in a data processing system environment have been supplied with uninterruptible power supplies. Such uninterruptible power supplies have been designed where the primary commercial power source and the reserve power source are connected in parallel. Both the primary power source and the reserve power source are continuously operated and both sources contribute to the energizing of the load.
In a prior uninterruptible power supply arrangement, the power supply includes a commercial A. C. line power source and a D. C. voltage energized inverter power source connected in parallel to a switching mechanism which alternately couples one or the other of the two power supplies to a load to be energized. The auxiliary power source comprising the inverter must be synchronized in frequency with the A. C. power line signal which requires complicated synchronizing circuitry.
It is therefore a principal object of this invention to provide a circuit for synchronizing the transfer of power signals to a load between an inverter and an A. C. line source.
It is another object of this invention to provide a circuit for generating synchronizing signals which will allow an inverter to be switched in and out of phase with the line A. C. power signal within one-half cycle of operation.
It is a further object of this invention to provide a circuit for generating signals used in synchronizing the operation of the inverter which is simple in construction and low in cost.